1. Field of the Invention
The present invention relates to improvements of board housing cases relevant to electronic circuit boards, for example, for vehicle-mounted electronic control devices and, more particularly, relates to an improved structure of a board housing case for a vehicle-mounted electronic device in which the heat generated from heating components mounted on a circuit board is efficiently diffused to a steel case by heat transfer and radiation to perform heat dissipation from both of a pair of a base and a cover that constitute the steel case to outside the case.
2. Description of the Related Art
A circuit board mounted with heating components is hermetically-sealed and housed in a steel case that is composed of a base and a cover, the heat generated from the heating components is transferred by coming into contact with the base or the cover via a heat transfer material and the generated heat is made to indirectly dissipate as the radiated heat to the inner surface of the base or the cover, the inner surface being coated in black; and accordingly, a temperature rise of the heating components is suppressed.
For example, as a conventional one, according to “ELECTRONIC CONTROL DEVICE FOR ENGINE CONTROL” disclosed in the following Patent Document 1, a circuit board mounted with a plurality of heating components is hermetically-sealed and housed in a steel case that is composed of a cover (referred to as a “base” in the present application) and a case (referred to as a “cover” in the present application) and the generated heat of a major heating component provided on the cover (base) side is transferred by coming into contact with the cover (base) via a heat transfer material. At the same time, the generated heat is made to indirectly dissipate as the radiated heat by coating the inner surface of the cover (base) in black and the generated heat of a small heating component provided on the case (cover) side is further made to indirectly dissipate to the inner surface of the case (cover) coated in black as the radiated heat; and accordingly, a temperature rise of the heating component is suppressed.
In addition, as other conventional one, according to “ELECTRONIC DEVICE” disclosed in the following Patent Document 2, a circuit board mounted with a heating component is hermetically-sealed and housed in a steel case that is composed of a base and a case (referred to as the “cover” in the present application) and the generated heat of the heating component provided on the case (cover) side is transferred by coming into contact with the base disposed on the opposite surface via a heat transfer material. In this case, any heat radiation to the inner surface of the base or the case (cover) is not taken into consideration. Incidentally, the case (cover) is formed in an uneven shape of a tall flat portion and a short flat portion and the heating component is disposed opposite to the tall flat portion.
Furthermore, as other conventional one, according to “MOUNTING STRUCTURE OF ELECTRONIC BOARD” disclosed in the following Patent Document 3, the concept of a thermal via and an isolated projection is shown. The thermal via serves as a heat transferring through hole which is for transferring and dissipating the generated heat of a heating component mounted on one surface of a circuit board to a heat transfer base provided on the other surface of the circuit board, and the isolated projection constitutes a small gap which is for filling a heat transfer material.
Further, as other conventional one, according to “ELECTRONIC BOARD DEVICE” disclosed in the following Patent Document 4, the concept of a portion passing through aboard (hereinafter, referred to as a “board pass through portion”) and an isolated projection is shown. The board pass through portion is for transferring and dissipating the generated heat of a heating component mounted on one surface of a circuit board to a central projection portion of a heat transfer base provided on the other surface of the circuit board, and the isolated projection constitutes a small gap which is for filling a heat transfer material. Incidentally, in the case of Patent Document 4, the configuration thereof is such that the generated heat of the heating component is transferred by coming into contact with both sides of the base side and the cover side via heat transfer materials, the cover is formed in an uneven shape of a tall flat portion and a short flat portion, and the heating component is disposed opposite to the short flat portion.